Composition, method and device for applying a coating on a support

Abstract

A composition for applying a coating on a support at low temperature from a dispersion of at least a component of the coating to be deposited in the composition. The composition includes at least a strong and heavy solvent with a boiling point higher than 150° C. approximately, and a weak solvent with a boiling point less than 100° C. approximately. The solvents forming the composition must constitute a mixture that evaporates at a temperature less than 100° C. The composition is particularly useful for forming electrodes or electrolyte in lithium-ion batteries. The method and the device used for forming the coating use a dispersion spreader and an infrared lamp.

1 . Composition permitting an application of a coating on a support at low temperature from a dispersion in said composition, of at least one component to be deposited on said support, said composition comprising at least one strong and heavy solvent in which the boiling temperature is higher than about 150° C. and a weak solvent in which the boiling temperature is lower than about 100° C., the strong and heavy solvent and the weak solvent, constituting a mixture which evaporates at a temperature lower that about 100° C.  
     
     
         2 . Composition according the  claim 1 , characterized in that is also comprises a diluting agent in which the boiling temperature is lower than about 80° C., said diluting agent having the property of increasing the solubilization capacity of the mixture and of facilitating an evaporation of the strong solvent at low temperature.  
     
     
         3 . Composition according to  claim 1 , characterized in that said mixture may evaporate under infrared to leave only said component constituting said coating on the support.  
     
     
         4 . Composition according to  claim 1 , characterized in that the strong and heavy solvent is selected from N-methyl pyrolidone and cyclopentanone.  
     
     
         5 . Composition according to  claim 1  or  5 , characterized in that the weak solvent is selected from acetone or ethyl acetate.  
     
     
         6 . Composition according to  claim 2 , characterized in that the diluting agent is selected from toluene or benzene.  
     
     
         7 . Composition according to  claim 2 , characterized in that the volume ratio of the mixture comprises less than 20% strong solvent, between 40% and 60% of weak solvent and between 15% and 25% diluting agent.  
     
     
         8 . Composition according to  claim 1 , characterized in that the component is present in the dispersion at the rate of 0.015 g/cc to 0.04 g/cc of the mixture.  
     
     
         9 . Composition according to  claim 1 , characterized in that the percentage volume ratio weak solvent/diluting agent is between 80/20 and 65/25.  
     
     
         10 . Composition according to  claim 1 , also comprising a binder for said component.  
     
     
         11 . Composition according to  claim 10 , characterized in that the binder comprises fluorinated polyvinylidene.  
     
     
         12 . Dispersion of a component to be deposited on a support in a composition according to anyone of  claims 1  to  11 .  
     
     
         13 . Dispersion according to  claim 12 , characterized in that said component comprises a graphite powder.  
     
     
         14 . Dispersion according to  claim 13 , characterized in that the weight ratio between the graphite powder and said composition varies between 60:10 and 90:10.  
     
     
         15 . Dispersion according to  claim 13 , characterized in that said component also comprises cobalt oxide.  
     
     
         16 . Process of applying a coating on a support characterized by the following steps: 
 (a) there is provided a composition comprising at least one strong and heavy solvent in which the boiling temperature is higher than about 150° C. and a weak solvent in which the boiling temperature is lower that about 100° C., the strong solvent and the weak solvent being present in ratio capable of constituting a mixture that can evaporate at a temperature lower than 100° C.;    (b) a component to be applied in the form of a coating on said support is dispersed in said mixture;    (c) the dispersion obtained in (b) is spreaded on said support;    (d) the dispersion is dried to obtain said coating.    
     
     
         17 . Process according to  claim 16 , characterized in that said dispersion is dried at a temperature lower than 100° C.  
     
     
         18 . Process according to  claim 16 , characterized in that said dispersion is dried by means of a heating element.  
     
     
         19 . Process according to  claim 16 , characterized said dispersion is dried by means of an infrared lamp.  
     
     
         20 . Process according to  claim 16 , characterized in that said dispersion is dried by means of an infrared lamp and a heating element.  
     
     
         21 . Process according to  claim 16 , characterized in that a binder of said component is added into said composition during step (a).  
     
     
         22 . Process according to  claim 21 , characterized in that the binder is first solubilized in the strong and heavy solvent then the weak solvent is mixed with a diluting agent, and the composition is thereafter mixed.  
     
     
         23 . Process according to  claim 16 , characterized in that the support is an electrode or an electrolyte in the form of film for rechargeable electrochemical generator.  
     
     
         24 . Device for applying a coating on a support in the form of a film comprising 
 a source of film support;    a feeding tank designed to contain a dispersion according to  claims 1  to  15 ;    unwinding means allowing to circulate the film support in the vicinity of the feeding tank;    means enabling to continuously pour a predetermined quantity of dispersion on the film support when the latter is passed in the vicinity of the feeding tank receiving means, and a winding means continuously transmitting the film support and it coating to the receiving means;    motor means designed to operate the unwinding means, the receiving means and the winding means; and    a heating device enabling to evaporate the liquid content of the dispersion at a temperature lower than 100° C. leaving a solid coating on said film support.    
     
     
         25 . Device according to  claim 24 , characterized in that the heating device comprises at least one infrared lamp.  
     
     
         26 . Device according to  claim 25 , characterized in that the film support consists of a cross-linkable polymer, and the heating device also comprises at least one ultraviolet lamp capable of cross-linking the cross-linkable polymer.  
     
     
         27 . Device according to  claim 24 , characterized in that the feeding tank includes a means enable to adjust the width as well as the thickness of a deposit of said dispersion on said film support according to predetermined parameters.